Speed and call quality testMy IP addressIP subnet calculatorDNS reportWhoIs lookupRemote support

Internet and network

Speed and call quality testTest delay, jitter and speed, with a focus on phone calls.My IP addressYour public IPv4 and IPv6 addresses, provider and address range.WhoIs lookupWho owns a domain or IP address, when it expires, and its DNS.DNS reportEvery DNS record for a domain, with email setup checked.IP subnet calculatorWork out a network's range, mask and hosts, and split it into subnets.

Computers and devices

Update checkIs this computer, phone and browser up to date? With links to update.Camera and mic testCheck your webcam and microphone before a call.Test print pagePrint an A4 page to check a printer: edges, text, line art and colours.

Make and print

Clean textStrip hidden characters, smart quotes and odd spaces from pasted text.QR code makerMake a QR code for a link, contact or message. Nothing leaves your browser.Wi-Fi QR posterPrint an A4 poster that lets guests join your Wi-Fi by scanning.

Surftec support

Remote supportLet a Surftec engineer connect to your computer to help you.All workingA full-screen confirmation that everything is up and running.

Surftec

Surftec websiteServices, news and how to contact Surftec
Cloud Tools
Guest
GuestNot signed in

Surftec customers will be recognised automatically when they use these tools from their office network.

Customer sign-in is coming soon.

IP subnet calculator

Type an address with its prefix or mask to see the network, its usable range and masks. Split it into smaller subnets, or look up any prefix in the reference tables.

Prefix/7
Addresses2^121
/64 networks2^57
Network
2c00::/7
First address
2c00::
Last address
2dff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
Addresses
2,658,455,991,569,831,745,807,614,120,560,689,152 (2^121)
/64 networks (LANs)
144,115,188,075,855,872 (2^57)
Full form
2c00:0000:0000:0000:0000:0000:0000:0000
Type
Global unicast 2000::/3
Public internet addresses
Reverse DNS zones
c.2.ip6.arpa
d.2.ip6.arpa
/7 is not on a 4-bit boundary, so it takes 2 /8 zones.
Split into smaller subnets/16
/8 (2)/9 (4)/10 (8)/11 (16)/12 (32)/16 (512)/20 (8,192)

2c00::/7 makes 512 subnets of /16; the first 256 are listed.

Subnets
#SubnetLast address
12c00::/162c00:ffff:ffff:ffff:ffff:ffff:ffff:ffff
22c01::/162c01:ffff:ffff:ffff:ffff:ffff:ffff:ffff
32c02::/162c02:ffff:ffff:ffff:ffff:ffff:ffff:ffff
42c03::/162c03:ffff:ffff:ffff:ffff:ffff:ffff:ffff
52c04::/162c04:ffff:ffff:ffff:ffff:ffff:ffff:ffff
62c05::/162c05:ffff:ffff:ffff:ffff:ffff:ffff:ffff
72c06::/162c06:ffff:ffff:ffff:ffff:ffff:ffff:ffff
82c07::/162c07:ffff:ffff:ffff:ffff:ffff:ffff:ffff
92c08::/162c08:ffff:ffff:ffff:ffff:ffff:ffff:ffff
102c09::/162c09:ffff:ffff:ffff:ffff:ffff:ffff:ffff
112c0a::/162c0a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
122c0b::/162c0b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
132c0c::/162c0c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
142c0d::/162c0d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
152c0e::/162c0e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
162c0f::/162c0f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
172c10::/162c10:ffff:ffff:ffff:ffff:ffff:ffff:ffff
182c11::/162c11:ffff:ffff:ffff:ffff:ffff:ffff:ffff
192c12::/162c12:ffff:ffff:ffff:ffff:ffff:ffff:ffff
202c13::/162c13:ffff:ffff:ffff:ffff:ffff:ffff:ffff
212c14::/162c14:ffff:ffff:ffff:ffff:ffff:ffff:ffff
222c15::/162c15:ffff:ffff:ffff:ffff:ffff:ffff:ffff
232c16::/162c16:ffff:ffff:ffff:ffff:ffff:ffff:ffff
242c17::/162c17:ffff:ffff:ffff:ffff:ffff:ffff:ffff
252c18::/162c18:ffff:ffff:ffff:ffff:ffff:ffff:ffff
262c19::/162c19:ffff:ffff:ffff:ffff:ffff:ffff:ffff
272c1a::/162c1a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
282c1b::/162c1b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
292c1c::/162c1c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
302c1d::/162c1d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
312c1e::/162c1e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
322c1f::/162c1f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
332c20::/162c20:ffff:ffff:ffff:ffff:ffff:ffff:ffff
342c21::/162c21:ffff:ffff:ffff:ffff:ffff:ffff:ffff
352c22::/162c22:ffff:ffff:ffff:ffff:ffff:ffff:ffff
362c23::/162c23:ffff:ffff:ffff:ffff:ffff:ffff:ffff
372c24::/162c24:ffff:ffff:ffff:ffff:ffff:ffff:ffff
382c25::/162c25:ffff:ffff:ffff:ffff:ffff:ffff:ffff
392c26::/162c26:ffff:ffff:ffff:ffff:ffff:ffff:ffff
402c27::/162c27:ffff:ffff:ffff:ffff:ffff:ffff:ffff
412c28::/162c28:ffff:ffff:ffff:ffff:ffff:ffff:ffff
422c29::/162c29:ffff:ffff:ffff:ffff:ffff:ffff:ffff
432c2a::/162c2a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
442c2b::/162c2b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
452c2c::/162c2c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
462c2d::/162c2d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
472c2e::/162c2e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
482c2f::/162c2f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
492c30::/162c30:ffff:ffff:ffff:ffff:ffff:ffff:ffff
502c31::/162c31:ffff:ffff:ffff:ffff:ffff:ffff:ffff
512c32::/162c32:ffff:ffff:ffff:ffff:ffff:ffff:ffff
522c33::/162c33:ffff:ffff:ffff:ffff:ffff:ffff:ffff
532c34::/162c34:ffff:ffff:ffff:ffff:ffff:ffff:ffff
542c35::/162c35:ffff:ffff:ffff:ffff:ffff:ffff:ffff
552c36::/162c36:ffff:ffff:ffff:ffff:ffff:ffff:ffff
562c37::/162c37:ffff:ffff:ffff:ffff:ffff:ffff:ffff
572c38::/162c38:ffff:ffff:ffff:ffff:ffff:ffff:ffff
582c39::/162c39:ffff:ffff:ffff:ffff:ffff:ffff:ffff
592c3a::/162c3a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
602c3b::/162c3b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
612c3c::/162c3c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
622c3d::/162c3d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
632c3e::/162c3e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
642c3f::/162c3f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
652c40::/162c40:ffff:ffff:ffff:ffff:ffff:ffff:ffff
662c41::/162c41:ffff:ffff:ffff:ffff:ffff:ffff:ffff
672c42::/162c42:ffff:ffff:ffff:ffff:ffff:ffff:ffff
682c43::/162c43:ffff:ffff:ffff:ffff:ffff:ffff:ffff
692c44::/162c44:ffff:ffff:ffff:ffff:ffff:ffff:ffff
702c45::/162c45:ffff:ffff:ffff:ffff:ffff:ffff:ffff
712c46::/162c46:ffff:ffff:ffff:ffff:ffff:ffff:ffff
722c47::/162c47:ffff:ffff:ffff:ffff:ffff:ffff:ffff
732c48::/162c48:ffff:ffff:ffff:ffff:ffff:ffff:ffff
742c49::/162c49:ffff:ffff:ffff:ffff:ffff:ffff:ffff
752c4a::/162c4a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
762c4b::/162c4b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
772c4c::/162c4c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
782c4d::/162c4d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
792c4e::/162c4e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
802c4f::/162c4f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
812c50::/162c50:ffff:ffff:ffff:ffff:ffff:ffff:ffff
822c51::/162c51:ffff:ffff:ffff:ffff:ffff:ffff:ffff
832c52::/162c52:ffff:ffff:ffff:ffff:ffff:ffff:ffff
842c53::/162c53:ffff:ffff:ffff:ffff:ffff:ffff:ffff
852c54::/162c54:ffff:ffff:ffff:ffff:ffff:ffff:ffff
862c55::/162c55:ffff:ffff:ffff:ffff:ffff:ffff:ffff
872c56::/162c56:ffff:ffff:ffff:ffff:ffff:ffff:ffff
882c57::/162c57:ffff:ffff:ffff:ffff:ffff:ffff:ffff
892c58::/162c58:ffff:ffff:ffff:ffff:ffff:ffff:ffff
902c59::/162c59:ffff:ffff:ffff:ffff:ffff:ffff:ffff
912c5a::/162c5a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
922c5b::/162c5b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
932c5c::/162c5c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
942c5d::/162c5d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
952c5e::/162c5e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
962c5f::/162c5f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
972c60::/162c60:ffff:ffff:ffff:ffff:ffff:ffff:ffff
982c61::/162c61:ffff:ffff:ffff:ffff:ffff:ffff:ffff
992c62::/162c62:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1002c63::/162c63:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1012c64::/162c64:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1022c65::/162c65:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1032c66::/162c66:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1042c67::/162c67:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1052c68::/162c68:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1062c69::/162c69:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1072c6a::/162c6a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1082c6b::/162c6b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1092c6c::/162c6c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1102c6d::/162c6d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1112c6e::/162c6e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1122c6f::/162c6f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1132c70::/162c70:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1142c71::/162c71:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1152c72::/162c72:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1162c73::/162c73:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1172c74::/162c74:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1182c75::/162c75:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1192c76::/162c76:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1202c77::/162c77:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1212c78::/162c78:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1222c79::/162c79:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1232c7a::/162c7a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1242c7b::/162c7b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1252c7c::/162c7c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1262c7d::/162c7d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1272c7e::/162c7e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1282c7f::/162c7f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1292c80::/162c80:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1302c81::/162c81:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1312c82::/162c82:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1322c83::/162c83:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1332c84::/162c84:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1342c85::/162c85:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1352c86::/162c86:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1362c87::/162c87:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1372c88::/162c88:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1382c89::/162c89:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1392c8a::/162c8a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1402c8b::/162c8b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1412c8c::/162c8c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1422c8d::/162c8d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1432c8e::/162c8e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1442c8f::/162c8f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1452c90::/162c90:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1462c91::/162c91:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1472c92::/162c92:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1482c93::/162c93:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1492c94::/162c94:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1502c95::/162c95:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1512c96::/162c96:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1522c97::/162c97:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1532c98::/162c98:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1542c99::/162c99:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1552c9a::/162c9a:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1562c9b::/162c9b:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1572c9c::/162c9c:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1582c9d::/162c9d:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1592c9e::/162c9e:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1602c9f::/162c9f:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1612ca0::/162ca0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1622ca1::/162ca1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1632ca2::/162ca2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1642ca3::/162ca3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1652ca4::/162ca4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1662ca5::/162ca5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1672ca6::/162ca6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1682ca7::/162ca7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1692ca8::/162ca8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1702ca9::/162ca9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1712caa::/162caa:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1722cab::/162cab:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1732cac::/162cac:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1742cad::/162cad:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1752cae::/162cae:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1762caf::/162caf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1772cb0::/162cb0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1782cb1::/162cb1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1792cb2::/162cb2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1802cb3::/162cb3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1812cb4::/162cb4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1822cb5::/162cb5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1832cb6::/162cb6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1842cb7::/162cb7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1852cb8::/162cb8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1862cb9::/162cb9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1872cba::/162cba:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1882cbb::/162cbb:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1892cbc::/162cbc:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1902cbd::/162cbd:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1912cbe::/162cbe:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1922cbf::/162cbf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1932cc0::/162cc0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1942cc1::/162cc1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1952cc2::/162cc2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1962cc3::/162cc3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1972cc4::/162cc4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1982cc5::/162cc5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
1992cc6::/162cc6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2002cc7::/162cc7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2012cc8::/162cc8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2022cc9::/162cc9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2032cca::/162cca:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2042ccb::/162ccb:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2052ccc::/162ccc:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2062ccd::/162ccd:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2072cce::/162cce:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2082ccf::/162ccf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2092cd0::/162cd0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2102cd1::/162cd1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2112cd2::/162cd2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2122cd3::/162cd3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2132cd4::/162cd4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2142cd5::/162cd5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2152cd6::/162cd6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2162cd7::/162cd7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2172cd8::/162cd8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2182cd9::/162cd9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2192cda::/162cda:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2202cdb::/162cdb:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2212cdc::/162cdc:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2222cdd::/162cdd:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2232cde::/162cde:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2242cdf::/162cdf:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2252ce0::/162ce0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2262ce1::/162ce1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2272ce2::/162ce2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2282ce3::/162ce3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2292ce4::/162ce4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2302ce5::/162ce5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2312ce6::/162ce6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2322ce7::/162ce7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2332ce8::/162ce8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2342ce9::/162ce9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2352cea::/162cea:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2362ceb::/162ceb:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2372cec::/162cec:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2382ced::/162ced:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2392cee::/162cee:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2402cef::/162cef:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2412cf0::/162cf0:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2422cf1::/162cf1:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2432cf2::/162cf2:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2442cf3::/162cf3:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2452cf4::/162cf4:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2462cf5::/162cf5:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2472cf6::/162cf6:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2482cf7::/162cf7:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2492cf8::/162cf8:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2502cf9::/162cf9:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2512cfa::/162cfa:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2522cfb::/162cfb:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2532cfc::/162cfc:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2542cfd::/162cfd:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2552cfe::/162cfe:ffff:ffff:ffff:ffff:ffff:ffff:ffff
2562cff::/162cff:ffff:ffff:ffff:ffff:ffff:ffff:ffff

IPv4 CIDR reference (/0 to /32)

IPv4 prefix lengths
PrefixSubnet maskWildcardAddressesUsable hostsSizeTypical use
/00.0.0.0255.255.255.2554,294,967,2964,294,967,29416,777,216 × /24
/1128.0.0.0127.255.255.2552,147,483,6482,147,483,6468,388,608 × /24
/2192.0.0.063.255.255.2551,073,741,8241,073,741,8224,194,304 × /24
/3224.0.0.031.255.255.255536,870,912536,870,9102,097,152 × /24
/4240.0.0.015.255.255.255268,435,456268,435,4541,048,576 × /24
/5248.0.0.07.255.255.255134,217,728134,217,726524,288 × /24
/6252.0.0.03.255.255.25567,108,86467,108,862262,144 × /24
/7254.0.0.01.255.255.25533,554,43233,554,430131,072 × /24
/8255.0.0.00.255.255.25516,777,21616,777,21465,536 × /24Old class A; 10.0.0.0/8
/9255.128.0.00.127.255.2558,388,6088,388,60632,768 × /24
/10255.192.0.00.63.255.2554,194,3044,194,30216,384 × /24
/11255.224.0.00.31.255.2552,097,1522,097,1508,192 × /24
/12255.240.0.00.15.255.2551,048,5761,048,5744,096 × /24172.16.0.0/12
/13255.248.0.00.7.255.255524,288524,2862,048 × /24
/14255.252.0.00.3.255.255262,144262,1421,024 × /24
/15255.254.0.00.1.255.255131,072131,070512 × /24
/16255.255.0.00.0.255.25565,53665,534256 × /24Old class B; 192.168.0.0/16
/17255.255.128.00.0.127.25532,76832,766128 × /24
/18255.255.192.00.0.63.25516,38416,38264 × /24
/19255.255.224.00.0.31.2558,1928,19032 × /24
/20255.255.240.00.0.15.2554,0964,09416 × /24
/21255.255.248.00.0.7.2552,0482,0468 × /24
/22255.255.252.00.0.3.2551,0241,0224 × /24Large office or guest Wi-Fi (1,022 hosts)
/23255.255.254.00.0.1.2555125102 × /24Larger office LAN (510 hosts)
/24255.255.255.00.0.0.2552562541 × /24Typical office LAN (old class C)
/25255.255.255.1280.0.0.1271281261/2 of a /24Smaller LAN or VLAN
/26255.255.255.1920.0.0.6364621/4 of a /24Smaller LAN or VLAN
/27255.255.255.2240.0.0.3132301/8 of a /24Small VLAN, phones, cameras
/28255.255.255.2400.0.0.1516141/16 of a /24Small VLAN, phones, cameras
/29255.255.255.2480.0.0.7861/32 of a /24Small fixed public block (5 usable)
/30255.255.255.2520.0.0.3421/64 of a /24Point-to-point (old style)
/31255.255.255.2540.0.0.1221/128 of a /24Point-to-point link (RFC 3021)
/32255.255.255.2550.0.0.0111/256 of a /24One host

IPv6 prefix reference

IPv6 prefix lengths
PrefixAddresses/64 LANs/48 sitesNibbleTypical use
/342,535,295,865,117,307,932,921,825,928,971,026,432 (2^125)2,305,843,009,213,693,95235,184,372,088,832NoAll global unicast (2000::/3)
/165,192,296,858,534,827,628,530,496,329,220,096 (2^112)281,474,976,710,6564,294,967,296Yes
/20324,518,553,658,426,726,783,156,020,576,256 (2^108)17,592,186,044,416268,435,456YesLarge provider allocation (RIPE minimum for some)
/29633,825,300,114,114,700,748,351,602,688 (2^99)34,359,738,368524,288NoRIPE allocation to a provider (often)
/3279,228,162,514,264,337,593,543,950,336 (2^96)4,294,967,29665,536YesProvider allocation (RIPE default)
/364,951,760,157,141,521,099,596,496,896 (2^92)268,435,4564,096Yes
/40309,485,009,821,345,068,724,781,056 (2^88)16,777,216256Yes
/4419,342,813,113,834,066,795,298,816 (2^84)1,048,57616Yes
/481,208,925,819,614,629,174,706,176 (2^80)65,5361YesOne site or organisation (RIPE PI / assignment)
/5275,557,863,725,914,323,419,136 (2^76)4,096Yes
/564,722,366,482,869,645,213,696 (2^72)256YesSmall site or home (common provider assignment)
/60295,147,905,179,352,825,856 (2^68)16YesSome home broadband (16 LANs)
/6418,446,744,073,709,551,616 (2^64)1YesOne LAN or VLAN (needed for SLAAC)
/7272,057,594,037,927,936 (2^56)1/256 of a /64Yes
/80281,474,976,710,656 (2^48)1/65,536 of a /64Yes
/964,294,967,2961/4,294,967,296 of a /64YesEmbeds an IPv4 address (NAT64)
/11265,5361/281,474,976,710,656 of a /64Yes
/1202561/72,057,594,037,927,936 of a /64Yes
/124161/1,152,921,504,606,846,976 of a /64Yes
/12641/4,611,686,018,427,387,904 of a /64No
/12721/9,223,372,036,854,775,808 of a /64NoPoint-to-point link (RFC 6164)
/12811/18,446,744,073,709,551,616 of a /64YesOne host or loopback

Private and special ranges

IPv4

Special-purpose ranges
RangeNameWhat it is
255.255.255.255/32Limited broadcastEvery host on the local network
0.0.0.0/8This networkNot routed; 0.0.0.0 means "any address" in settings
10.0.0.0/8Private (RFC 1918)Office and home networks; not routed on the internet
100.64.0.0/10Shared address space (CGNAT)Used by providers behind carrier-grade NAT (RFC 6598)
127.0.0.0/8LoopbackThis computer
169.254.0.0/16Link-local (APIPA)Self-assigned when no DHCP server answers
172.16.0.0/12Private (RFC 1918)Office and home networks; not routed on the internet
192.0.0.0/24IETF protocol assignmentsSpecial uses such as DS-Lite
192.0.2.0/24Documentation (TEST-NET-1)For examples; never used on a network
192.88.99.0/246to4 relay (deprecated)Formerly anycast for 6to4
192.168.0.0/16Private (RFC 1918)Office and home networks; not routed on the internet
198.18.0.0/15BenchmarkingNetwork equipment testing (RFC 2544)
198.51.100.0/24Documentation (TEST-NET-2)For examples; never used on a network
203.0.113.0/24Documentation (TEST-NET-3)For examples; never used on a network
224.0.0.0/4MulticastOne-to-many traffic, such as IPTV and routing protocols
240.0.0.0/4ReservedFuture use; not usable on most systems

IPv6

Special-purpose ranges
RangeNameWhat it is
::/128UnspecifiedNo address; :: means "any address" in settings
::1/128LoopbackThis computer
::ffff:0:0/96IPv4-mappedAn IPv4 address written as IPv6
64:ff9b::/96NAT64IPv4 addresses reached through a NAT64 gateway
100::/64Discard onlyTraffic sent here is dropped (RFC 6666)
2001:db8::/32DocumentationFor examples; never used on a network
2001::/32TeredoIPv6 tunnelled over IPv4 UDP
2002::/166to4IPv6 tunnelled over IPv4 (largely retired)
3fff::/20DocumentationFor examples (RFC 9637)
fc00::/7Unique local (ULA)Private IPv6, like RFC 1918; usually fd00::/8
fe80::/10Link-localEvery IPv6 interface has one; not routed
ff00::/8MulticastOne-to-many traffic; replaces broadcast
2000::/3Global unicastPublic internet addresses

About this tool

A network is written as an address and a prefix length, such as 192.168.1.0/24: the first 24 bits name the network and the rest number the devices on it. The calculator works out where the network starts and ends, how many devices it holds, its subnet and wildcard masks, and the reverse DNS zone to ask your provider for.

It also splits a network into equal smaller ones (one per VLAN or site), turns a range of addresses into the fewest CIDR blocks for a firewall rule, and lists every IPv4 prefix length and the common IPv6 ones in reference tables.

Common questions

Why are two addresses lost in every IPv4 subnet?

The first address names the network and the last is the broadcast address, so a /24 has 256 addresses but 254 for devices. A /31 (a link between two routers) and a /32 (one host) are the exceptions.

What size of IPv6 network should a LAN use?

Always /64. Devices pick their own address within it (SLAAC), which needs the full 64 bits. A site usually gets a /48 or /56 from its provider, which holds 65,536 or 256 LANs.

What is a wildcard mask?

The subnet mask turned inside out: 255.255.255.0 becomes 0.0.0.255. Cisco access lists and OSPF use it to say which bits must match.

Which ranges can I use inside an office?

IPv4: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. IPv6: unique local addresses from fd00::/8, though most networks use the public prefix from their provider.